[Field of the Invention]
The present invention relates to an apparatus that detects the deterioration of a photocoupler to which a predetermined alternating-current (AC) voltage is applied.
[Description of the Related Art]
Conventionally, there is a technology in which the output voltage of a photocoupler, to which a predetermined direct-current voltage is applied, is compared to a reference voltage by a comparator. The photocoupler is determined to have deteriorated when the output voltage of the photocoupler is lower than the reference voltage (refer to JP-A-2009-71928).
The technology described in JP-A-2009-71928 requires the addition of a power supply that generates the reference voltage and the comparator that compares the output voltage of the photocoupler to the reference voltage. Therefore, increase in circuit size is unavoidable. Determination of the deterioration of a photocoupler is also desired for photocouplers to which a predetermined alternating-current voltage is applied.